Arrangement of tubing in solar boiler panels

ABSTRACT

A boiler for a solar receiver includes a first boiler panel having a plurality of tubes fluidly connecting an inlet header of the first boiler panel to an outlet header of the first boiler panel. The tubes of the first boiler panel form a first solar receiver surface. A second boiler panel has a plurality of tubes fluidly connecting an inlet header of the second boiler panel to an outlet header of the second boiler panel. The tubes of the second boiler panel form a second solar receiver surface. The first and second boiler panels are adjacent to one another with a portion of the first boiler panel and an end of the first solar receiver surface overlapping an end of the second boiler panel to reduce solar radiation passing between the first and second solar receiver surfaces.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/552,724 filed on Sep. 2, 2009, which claimspriority to U.S. Provisional application No. 61/151,984, filed Feb. 12,2009, to U.S. Provisional application No. 61/152,011, filed Feb. 12,2009, to U.S. Provisional application No. 61/152,035, filed Feb. 12,2009, to U.S. Provisional application No. 61/152,049, filed Feb. 12,2009, to U.S. Provisional application No. 61/152,077, filed Feb. 12,2009, to U.S. Provisional application No. 61/152,114, filed Feb. 12,2009, and to U.S. Provisional application No. 61/152,286, filed Feb. 13,2009, each of which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to solar power production, and moreparticularly, to solar receiver panels for use in solar boilers.

2. Description of Related Art

Solar power generation has been considered a viable source to helpprovide for energy needs in a time of increasing consciousness of theenvironmental aspects of power production. Solar energy productionrelies mainly on the ability to collect and convert energy freelyavailable from the sun and can be produced with very little impact onthe environment. Solar power can be utilized without creatingradioactive waste as in nuclear power production, and without producingpollutant emissions including greenhouse gases as in fossil fuel powerproduction. Solar power production is independent of fluctuating fuelcosts and does not consume non-renewable resources.

Solar power generators generally employ fields of controlled mirrors,called heliostats, to gather and concentrate sunlight on a receiver toprovide a heat source for power production. A solar receiver typicallytakes the form of a panel of tubes conveying a working fluidtherethrough. Previous solar generators have used working fluids such asmolten salt because it has the ability to store energy, allowing powergeneration when there is no solar radiation. The heated working fluidsare typically conveyed to a heat exchanger where they release heat intoa second working fluid such as air, water, or steam. Power is generatedby driving heated air or steam through a turbine that drives anelectrical generator.

More recently, it has been determined that solar production can beincreased and simplified by using water/steam as the only working fluidin a receiver that is a boiler. This can eliminate the need for aninefficient heat exchanger between two different working fluids. Thisdevelopment has lead to new challenges in handling the intense solarheat without damage to the system. Typical boilers include two or moresections at different temperatures and pressures, such as a section ofsteam generator panels, a section of superheater panels, and a sectionof reheater panels, for example. In a solar boiler, it is advantageousto have boiler sections close together within the receiver where thefocused solar radiation provides heat. It has been known, for example,to have one section on top of another section. There is a gap betweensuch adjacent sections, which accommodates headers and associatedstructures of the boiler sections and can provide room for thermalexpansion and contraction of the boiler sections. The gap must beprotected against the possibility of focused sunlight reachingcomponents internal to the receiver panels (known as leakage), where theintense radiation can be harmful.

One approach to this problem has been to cover the gaps between boilersections with a thermal barrier or shield, which blocks the sunlightfrom entering the gap. Such a thermal barrier occupies surface area inthe key receiving area of the boiler and thus reduces the amount ofuseable solar radiation from the heliostats that is actually received bythe boiler.

While the known systems of solar power production have generally beenconsidered satisfactory for their intended purposes, there has remaineda need in the art for solar receivers that can improve the useablereceiving area while protecting internal spaces from leakage of solarradiation, allowing for thermal contraction and expansion, and providingfor drainability. There also has remained a need in the art for suchsolar receivers that are easy to make and use. The present inventionprovides a solution to these problems.

SUMMARY OF THE INVENTION

The subject invention is directed to a new and useful boiler for a solarreceiver. The boiler includes a first boiler panel having a plurality oftubes fluidly connecting an inlet header of the first boiler panel to anoutlet header of the first boiler panel. The tubes of the first boilerpanel form a first solar receiver surface and a first internal surfaceopposite the first solar receiver surface. A second boiler panel has aplurality of tubes fluidly connecting an inlet header of the secondboiler panel to an outlet header of the second boiler panel. The tubesof the second boiler panel form a second solar receiver surface and asecond internal surface opposite the second solar receiver surface. Thefirst and second boiler panels are adjacent to one another with aportion of the first boiler panel and an end of the first solar receiversurface overlapping an end of the second boiler panel to reduce solarradiation passing between the first and second solar receiver surfaces.

In certain embodiments, the first and second boiler panels are adjacentto one another with an end of the first solar receiver surfaceoverlapping an end of the second boiler panel so as to cover at leastone of the headers behind the first solar receiver surface. It is alsocontemplated that an end of the first solar receiver surface can overlapan end of the second boiler panel so as to cover one of the headers ofeach boiler panel behind the first solar receiver surface.

The first and second internal surfaces can be covered with an insulationlayer. A gap can be provided between the end of the second boiler paneland the portion of the first boiler panel overlapping the end of thesecond boiler panel to accommodate relative movement of the first andsecond boiler panels due to thermal growth, and the gap can belabyrinthine. The tubes of the first and second panels can be configuredand adapted to be fully drainable by way of at least one header in eachpanel. It is also contemplated that the portion of the first solarreceiver panel overlapping the end of the second boiler panel caninclude a 180° bend in the uppermost end of the plurality of tubes ofthe first solar receiving panel.

The invention also includes a boiler for a solar receiver includingsteam generator, superheater, and reheater panels, each having aplurality of tubes fluidly connecting a respective inlet header and arespective outlet header. The tubes of each panel form a solar receiversurface and opposed internal surface. The steam generator andsuperheater panels are adjacent one another with a portion of the steamgenerator panel and an end of the solar receiver surface thereofoverlapping an end of the superheater panel to reduce solar radiationpassing between the solar receiver surfaces of the steam generator andsuperheater panels. The steam generator and reheater panels are adjacentone another with a portion of the reheater panel including an end of thesolar receiver surface thereof overlapping an end of the steam generatorpanel to reduce solar radiation passing between the solar receiversurfaces of the steam generator and reheater panels.

These and other features of the systems and methods of the subjectinvention will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject inventionappertains will readily understand how to make and use the devices andmethods of the subject invention without undue experimentation,preferred embodiments thereof will be described in detail herein belowwith reference to certain figures, wherein:

FIG. 1 a is side elevation view of a gap between boiler sections in atypical prior art solar boiler;

FIG. 2 is a side elevation view of a portion of an exemplary embodimentof a boiler constructed in accordance with the present invention,showing the overlap region between two receiver surfaces;

FIG. 3 is an interior elevation view of the portion of the boiler ofFIG. 2, showing the headers and the interior surfaces of the tubes inthe boiler panels;

FIG. 4 is a perspective view of a portion of the boiler of FIG. 2,showing the overlap configuration of two adjacent boiler panels;

FIG. 5 is a side elevation view of a portion of the boiler of FIG. 2,showing the overlap regions between adjacent superheater, steamgenerator, and reheater panels; and

FIG. 6 is a side elevation view of a portion of the boiler of FIG. 2,showing another configuration for the end tubes of the panels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectinvention. For purposes of explanation and illustration, and notlimitation, a partial view of an exemplary embodiment of a boilerconstructed in accordance with the invention is shown in FIG. 2 and isdesignated generally by reference character 100. Other embodiments of aboiler in accordance with the invention, or aspects thereof, areprovided in FIGS. 3-5, as will be described. The systems of theinvention can be used to increase the effective receiving area whileprotecting internal spaces and components in boilers, for example insolar power generation.

Solar boilers are set up in such a way that there are at least twodistinct tube sections: one is a steam generator section containingboiling water and one or more is a superheating section containingsuperheated steam. FIG. 1 shows an example of a solar boiler 10 having asteam generator section 14 and a superheater section 12. These sectionsreceive solar energy on their exterior surface during operation, asindicated by straight arrows in FIG. 1. It is required that the tubingin these different sections of tubes be physically separated from oneanother, e.g., where the headers 16 and 18 of the respective sections 12and 14 are located in FIG. 1. Previous designs have had the ends ofadjacent areas, including adjacent headers, close together. But even thebest designs leave a significant gap between the solar receiver surfacesof sections 12 and 14 that would allow direct solar radiation to leakbetween the two tube sections. Therefore, this gap area must beprotected with a thermal barrier, such as barrier 20. As indicated inFIG. 1 by a bent arrow, barrier 20 protects the gap region by blockingthe incident solar radiation. This protection comes at a cost, namelythe waste of concentrated solar energy in the receiving area that isincident on barrier 20 instead of on a receiver surface of sections 12and 14.

With reference to FIG. 2, there are shown features of a solar boiler 100constructed in accordance with the present invention. Boiler 100 for asolar receiver includes a first boiler panel 102 having a plurality oftubes fluidly connecting an inlet header 113 of the first boiler panel(not shown in FIG. 2, but see, FIG. 5) to an outlet header 104 of firstboiler panel 102. The tubes of first boiler panel 102 form a first solarreceiver surface 106 and a first internal surface 108 opposite firstsolar receiver surface 106. The exterior receiver surface 106 receivessolar energy, for example from a field of heliostats, as indicated byarrows in FIG. 2.

A second boiler panel 110 similarly includes a plurality of tubesfluidly connecting an inlet header 112 of second boiler panel 110 to anoutlet header 114 of second boiler panel 110. The tubes of second boilerpanel 110 form a second solar receiver surface 116 and a second internalsurface 118 opposite second solar receiver surface 116 (i.e. exteriorand interior surfaces, as indicated in FIG. 2). Like receiver surface106, exterior receiver surface 116 receives solar energy, for examplefrom a field of heliostats, as indicated by arrows in FIG. 2.

First and second boiler panels 102 and 110 are adjacent one another withan end portion 120 of first boiler panel 102 and the corresponding endportion of first solar receiver surface 106 overlapping an end 122 ofsecond boiler panel 110 to reduce or prevent solar radiation passing inbetween the first and second solar receiver surfaces 106 and 116 intothe interior space of boiler 100. Interior surfaces 108 and 118 have alayer of insulating material 124 to protect the interior space of boiler100 and components therein from the high temperatures on the backside ofthe tubes.

FIG. 3 shows the same portion of boiler 100 as in FIG. 2 but from theinterior, with insulating material 124 removed to show the tubes andheaders of panels 102 and 110. FIG. 4 shows a perspective view of theoverlap region from the interior with the insulating material 124removed as well. While the example described above includes shieldingheaders 112 and 104 shielded behind first receiver surface 106, thoseskilled in the art will readily appreciate that each panel can cover itsown header, or any other suitable overlap configuration can be usedwithout departing from the spirit and scope of the invention.

In this unique design, the tubes, which comprise the receiving surfaces106 and 116, are overlapped in such a way that there is no need for abarrier to cover a gap between the receiving surfaces 106 and 116. Thisis accomplished by overlapping portions of the tubes of different boilersections as described above. An overlapping tube design, in accordancewith the present invention, prevents the need for wasteful insulation orshielding covering external portions of the receiver area of boiler 100.This also allows for a higher amount of absorption of solar radiation,which increases the overall efficiency of the system.

As indicated by arrows in FIG. 2, the overlap region between panels 102and 110 allows for thermal expansion and contraction of the panels.There is a gap 121 between end portion 120 of boiler panel 102 and endportion 122 of boiler panel 110. As can be seen in FIG. 2, gap 121 islabyrinthine and thus any leakage of solar radiation is absorbed by theboiler tubes, e.g., in end portion 122, and is not allowed to penetratethe interior space of boiler 100. Since end 120 of first panel 102 andend 122 of second panel 110 spaced apart from one another, panels 102and 110 can move relative to one another during the thermal expansionand contraction that results from the daily cycle of solar radiationincident on the receiver area of boiler 100. Thus, while gap 121accommodates thermal expansion and contraction, in terms of leakage ofsolar radiation there is effectively no gap between panels 102 and 110.

If boiler panels are exposed to ambient conditions, it can be necessaryto drain the water from the tubing after sunset to prevent damage fromfreezing water in the tubes. In tubes 102 and 110 this draining can beaccomplished through drains 170, as indicated schematically in FIG. 2.The unique overlapping design of ends 120 and 122 allows the tubes ofpanels 102 and 110 to be completely drainable, as there is a header ateach low point for each panel 102 and 110. The 180° bend in end 120 offirst panel 102 does not trap water during draining, since water on bothsides of the bend can flow downward to a drain or header. If, forexample, if there were a 180° bend at the very bottom of a panel, itcould trap water during draining and such a panel would not be fullydrainable.

As shown in FIG. 4, there are two or three end tubes 191 on each end ofheaders 112 and 104. End tubes 191 are bent inward to shorten theoverall length of the respective headers 112 and 104. If it is desiredto make end tubes 191 fully drainable, this can be accomplished usingthe configuration shown in FIG. 6. FIG. 6 shows the locations 193 and194 of fully drainable end tubes for panels 110 and 102, respectively.Those skilled in the art will readily appreciate that any suitable endtube configuration can be used for panel headers without departing fromthe spirit and scope of the invention.

With reference now to FIG. 5, panel 102 is a steam generator panel andpanel 110 is a superheater panel. Boiler 100 also includes reheaterpanel 140. Each reheater panel 140 includes a plurality of tubes fluidlyconnecting an inlet header 117 to an outlet header 115, much asdescribed above with respect to panels 102 and 110. Panel 140 overlapspanel 102 in the same manner as panel 102 overlaps panel 110 asdescribed above. It is to be understood that boiler 100 includesmultiple, parallel panels of each type, as indicated in FIG. 4. Multiplesets of overlapped panels 102, 110, and 140 can be arranged into aboiler wall, as in FIG. 4. Multiple boiler walls can be joined, forexample to form a four-sided or multi-sided boiler capable of receivingconcentrated solar energy from heliostats surrounding the base of theboiler. While described herein in the context of a three-stage boiler,those skilled in the art will readily appreciate that any suitablenumber of stages can be used, and can be arranged in any suitable mannerwithout departing from the spirit and scope of the invention.

The methods and systems of the present invention, as described above andshown in the drawings provide for increased effective area for receivingsolar radiation in a boiler, such as in a solar receiver. Thisconfiguration provides improved efficiency while also providingprotection of components and spaces internal to the receiver panels fromleakage of solar radiation from the heliostats, while allowing forthermal expansion and contraction as well as drainability of the boilersections.

While the apparatus and methods of the subject invention have been shownand described with reference to preferred embodiments, those skilled inthe art will readily appreciate that changes and/or modifications may bemade thereto without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A boiler for a solar receiver comprising: a) afirst boiler panel having a plurality of tubes fluidly connecting aninlet header of the first boiler panel to an outlet header of the firstboiler panel, the tubes of the first boiler panel defining alongitudinal tube direction and forming a first solar receiver surfaceand a first internal surface opposite the first solar receiver surface;and b) a second boiler panel having a plurality of tubes fluidlyconnecting an inlet header of the second boiler panel to an outletheader of the second boiler panel, the tubes of the second boiler panelforming a second solar receiver surface and a second internal surfaceopposite the second solar receiver surface, wherein the first and secondboiler panels are adjacent one another with a portion of the tubes ofthe first boiler panel at an end of the first solar receiver surfaceoverlapping the tubes of the second boiler panel at an end of the secondboiler panel in the longitudinal tube direction to reduce solarradiation passing between the first and second solar receiver surfaces.2. A boiler for a solar receiver as recited in claim 1, wherein thefirst and second boiler panels are adjacent to one another with an endof the first solar receiver surface overlapping an end of the secondboiler panel so as to cover at least one of the headers behind the firstsolar receiver surface.
 3. A boiler for a solar receiver as recited inclaim 1, wherein the first and second boiler panels are adjacent to oneanother with an end of the first solar receiver surface overlapping anend of the second boiler panel so as to cover one of the headers of eachboiler panel behind the first solar receiver surface.
 4. A boiler for asolar receiver as recited in claim 1, wherein the first and secondinternal surfaces are covered with an insulation layer.
 5. A boiler fora solar receiver as recited in claim 1, wherein a gap is providedbetween the end of the second boiler panel and the portion of the firstboiler panel overlapping the end of the second boiler panel toaccommodate relative movement of the first and second boiler panels dueto thermal growth.
 6. A boiler for a solar receiver as recited in claim1, wherein the tubes of the first and second panels are configured andadapted to be fully drainable by way of at least one header in eachpanel.
 7. A boiler for a solar receiver comprising: a) a steam generatorpanel having a plurality of tubes fluidly connecting an inlet header andan outlet header of the steam generator panel, the tubes of the steamgenerator panel defining a longitudinal tube direction and forming asolar receiver surface and opposed internal surface; b) a superheaterpanel having a plurality of tubes fluidly connecting an inlet header andan outlet header of the superheater panel, the tubes of the superheaterpanel forming a solar receiver surface and opposed internal surface,wherein the steam generator and superheater panels are adjacent oneanother with a portion of the tubes of the steam generator panel at anend of the solar receiver surface thereof overlapping the tubes of thesuperheater panel at an end of the superheater panel in the longitudinaltube direction to reduce solar radiation passing between the solarreceiver surfaces of the steam generator and superheater panels; and c)a reheater panel having a plurality of tubes fluidly connecting an inletheader and an outlet header of the reheater panel, the tubes of thereheater panel forming a solar receiver surface and opposed internalsurface, wherein the steam generator and reheater panels are adjacentone another with a portion of the tubes of the reheater panel at an endof the solar receiver surface thereof overlapping the tubes of the steamgenerator panel at an end of the steam generator panel in thelongitudinal tube direction to reduce solar radiation passing betweenthe solar receiver surfaces of the steam generator and reheater panels.8. A boiler for a solar receiver as recited in claim 7, wherein thesteam generator and superheater panels are adjacent one another with anend of the solar receiver surface of the steam generator paneloverlapping an end of the superheater panel so as to cover one header ofeach of the steam generator and superheater panels behind the solarreceiver surface of the steam generator panel, and wherein the steamgenerator and reheater panels are adjacent one another with an end ofthe solar receiver surface of the reheater panel overlapping an end ofthe steam generator panel so as to cover one header of each of the steamgenerator and reheater panels behind the solar receiver surface of thereheater panel.
 9. A boiler for a solar receiver as recited in claim 7,wherein the internal surfaces of the steam generator, superheater, andreheater panels are covered with an insulation layer.
 10. A boiler for asolar receiver as recited in claim 7, wherein a first labyrinthine gapis provided between the end of the superheater panel and the portion ofthe steam generator panel overlapping the end of the superheater panelto accommodate relative movement of the steam generator and superheaterpanels due to thermal growth, and wherein a second labyrinthine gap isprovided between the end of the steam generator panel and the portion ofthe reheater panel overlapping the end of the steam generator panel toaccommodate relative movement of the steam generator and reheater panelsdue to thermal growth.
 11. A boiler for a solar receiver as recited inclaim 7, wherein the tubes of the steam generator, superheater, andreheater panels are configured and adapted to be fully drainable by wayof at least one header in each panel.
 12. A boiler for a solar receivercomprising: a) a first boiler panel having a plurality of tubes fluidlyconnecting an inlet header of the first boiler panel to an outlet headerof the first boiler panel, the tubes of the first boiler panel defininga longitudinal tube direction and forming a first solar receiver surfaceand a first internal surface opposite the first solar receiver surface;and b) a second boiler panel having a plurality of tubes fluidlyconnecting an inlet header of the second boiler panel to an outletheader of the second boiler panel, the tubes of the second boiler panelforming a second solar receiver surface and a second internal surfaceopposite the second solar receiver surface, wherein the first and secondboiler panels are adjacent one another with a portion of the tubes ofthe first boiler panel at an end of the first solar receiver surfaceoverlapping the tubes of the second boiler panel at an end of the secondboiler panel in the longitudinal tube direction and covering one headerof each of the first and second boiler panels, and wherein alabyrinthine gap is provided between the end of the first solar receiversurface and the end of the second boiler panel to accommodate relativemovement of the first and second boiler panels due to thermal growth.13. A boiler for a solar receiver as recited in claim 12, wherein thetubes of the first and second panels are configured and adapted to befully drainable by way of at least one header in each panel.
 14. Aboiler for a solar receiver as recited in claim 12, wherein the portionof the first solar receiver panel overlapping the end of the secondboiler panel includes a 180° bend in the uppermost end of the pluralityof tubes of the first solar receiving panel.